The present invention relates to a radial tire which can control vehicle wandering.
In a radial tire in which a belt reinforcement layer, for example, a steel cord layer is disposed radially outwardly of the carcass, the rigidity of a tread portion becomes higher in the shoulder regions due to the hoop effect of the belt reinforcement and also the thicker tread rubber. Accordingly, the shoulder regions largely effect the occurrence of vehicle wadering when running on a road in which the surface is partially inclined in the side direction. Further, for example, when such a tire mounted on the steering axis of a vehicle runs across a step difference A in the road level such as a rut, a railway and the like, as shown in FIG. 6(a), if the side of the tire shoulder B bumps against the differnce A, the tire T changes from its travel course, and the vehicle can not ride over the difference without applying more steering.
Therefore, to round the tire shoulder B as shown in FIG. 6(b) and to form axial sipes in the tire shoulder B to reduce the rubber rigidity thereof have been proposed.
In the former situation, however, the higher rigidity of the tire shoulder still produces a wadering phenomenon and also a rather strong reaction against the riding-over operation, which worsens the ride.
In the latter situation, uneven wear such as the so-called heel and toe wear is apt to be produced in the tread should regions, which shorten the tire life.